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Sustainable energy, such as sunlight and wind energy, that comes from sources that do not need to be replenished has become important. Accordingly, the importance of the design and stable management of DC microgrids is also increasing. From this point of view, this paper analyzes the interaction between source and load converters constituting the DC microgrid using the derived mathematical input and output impedances models. This paper proposes a stability improvement method using the analyzed result. The method focuses on the presence or absence of input and output impedance overlap using Middlebrook’s stability criteria. To verify validity of the proposed method, a case study with three damping methods is conducted: (1) RC parallel damping with PR controller, (2) RL parallel damping with PR controller, and (3) RL series damping with PR controller. Additionally, the frequency domain characteristics and the Nyquist stability are analyzed using MATLAB, and simulation verification is conducted using PSIM. Through the analysis and simulation results, we confirm that the stability of the DC microgrid can be improved by applying the proposed method. The passive damping method analyzed in this paper is applied to an installed power converter, where it is possible to ensure the stability of the DC microgrid.
Jae-Suk Lee; Yeong-Jun Choi. A Stability Improvement Method of DC Microgrid System Using Passive Damping and Proportional-Resonance (PR) Control. Sustainability 2021, 13, 9542 .
AMA StyleJae-Suk Lee, Yeong-Jun Choi. A Stability Improvement Method of DC Microgrid System Using Passive Damping and Proportional-Resonance (PR) Control. Sustainability. 2021; 13 (17):9542.
Chicago/Turabian StyleJae-Suk Lee; Yeong-Jun Choi. 2021. "A Stability Improvement Method of DC Microgrid System Using Passive Damping and Proportional-Resonance (PR) Control." Sustainability 13, no. 17: 9542.
This paper covers the active voltage balancing method of secondary batteries. The number of applications using secondary batteries is increasing, and the batteries are normally connected in series/parallel to increase discharge cycle and power. The problem is that when there is a voltage imbalance between the cells or modules of a battery, there is a risk of an accident in the near-sighted way, shortening the life of the battery cells. Although this risk was prevented through passive balancing, this approach has limitations, including heat generation, long balancing time, and in the case of a battery that needs to be balanced between modules (or between stacks), its effectiveness decreases. Therefore, in this paper, an active cell balancing method that can overcome the limitations mentioned before is proposed. The proposed method uses a multi-winding transformer, and to increase the power density, the magnetizing inductance is decreased, and an auxiliary circuit is added. The validity of the proposed circuit was verified through mode analysis and simulation. In addition, waveforms showing the balancing performance under various conditions and the comparison results between conventional and proposed methods are given.
Young-Hwa Park; Rae-Young Kim; Yeong-Jun Choi. An Active Cascaded Battery Voltage Balancing Circuit Based on Multi-Winding Transformer with Small Magnetizing Inductance. Energies 2021, 14, 1302 .
AMA StyleYoung-Hwa Park, Rae-Young Kim, Yeong-Jun Choi. An Active Cascaded Battery Voltage Balancing Circuit Based on Multi-Winding Transformer with Small Magnetizing Inductance. Energies. 2021; 14 (5):1302.
Chicago/Turabian StyleYoung-Hwa Park; Rae-Young Kim; Yeong-Jun Choi. 2021. "An Active Cascaded Battery Voltage Balancing Circuit Based on Multi-Winding Transformer with Small Magnetizing Inductance." Energies 14, no. 5: 1302.
Microgrid construction is promoted globally to solve the problems of energy inequality in island regions and the use of fossil fuels. In the application of a microgrid system, it is important to calculate the capacities of renewable energy sources and storage systems (ESSs) to ensure economic feasibility. In some microgrids that have recently had environmental challenges, there are island regions where the policy is to consider both the installation of the microgrid system and the supplement of electric vehicles (EV). However, an EV load pattern that does not match the solar radiation pattern may increase the required ESS capacity. Therefore, in this study, we designed and analyzed a method for reducing the microgrid system cost using a controllable EV charging load without the requirements of vehicle-to-grid technology and real-time pricing. The power system operations at similar capacities of photovoltaic and ESS were shown by applying EV charging control steps in 10% increments to analyze the effect of EV charging demand control on the microgrid. As a result of the proposed simulation, the amount of renewable power generation increased by 2.8 GWh over 20 years only by moving the charging load under the same conditions. This is an effect that can reduce CO2 by about 2.1 kTon.
Sang Chae; Gi Kim; Yeong-Jun Choi; Eel-Hwan Kim. Design of Isolated Microgrid System Considering Controllable EV Charging Demand. Sustainability 2020, 12, 9746 .
AMA StyleSang Chae, Gi Kim, Yeong-Jun Choi, Eel-Hwan Kim. Design of Isolated Microgrid System Considering Controllable EV Charging Demand. Sustainability. 2020; 12 (22):9746.
Chicago/Turabian StyleSang Chae; Gi Kim; Yeong-Jun Choi; Eel-Hwan Kim. 2020. "Design of Isolated Microgrid System Considering Controllable EV Charging Demand." Sustainability 12, no. 22: 9746.
This paper proposes the modeling and design of a controller for an inductive power transfer (IPT) system with a semi-bridgeless active rectifier (S-BAR). This system consists of a double-sided Inductor-Capacitor-Capacitor (LCC) compensation network and an S-BAR, and maintains a constant output voltage under load variation through the operation of the rectifier switches. Accurate modeling is essential to design a controller with good performance. However, most of the researches on S-BAR have focused on the control scheme for the rectifier switches and steady-state analysis. Therefore, modeling based on the extended describing function is proposed for an accurate dynamic analysis of an IPT system with an S-BAR. Detailed mathematical analyses of the large-signal model, steady-state operating solution, and small-signal model are provided. Nonlinear large-signal equivalent circuit and linearized small-signal equivalent circuit are presented for intuitive understanding. In addition, worst case condition is selected under various load conditions and a controller design process is provided. To demonstrate the effectiveness of the proposed modeling, experimental results using a 100 W prototype are presented.
Hwa-Rang Cha; Rae-Young Kim; Kyung-Ho Park; Yeong-Jun Choi; Cha; Kim; Park; Choi; And Yeong-Jun Choi. Modeling and Control of Double-Sided LCC Compensation Topology with Semi-Bridgeless Active Rectifier for Inductive Power Transfer System. Energies 2019, 12, 3921 .
AMA StyleHwa-Rang Cha, Rae-Young Kim, Kyung-Ho Park, Yeong-Jun Choi, Cha, Kim, Park, Choi, And Yeong-Jun Choi. Modeling and Control of Double-Sided LCC Compensation Topology with Semi-Bridgeless Active Rectifier for Inductive Power Transfer System. Energies. 2019; 12 (20):3921.
Chicago/Turabian StyleHwa-Rang Cha; Rae-Young Kim; Kyung-Ho Park; Yeong-Jun Choi; Cha; Kim; Park; Choi; And Yeong-Jun Choi. 2019. "Modeling and Control of Double-Sided LCC Compensation Topology with Semi-Bridgeless Active Rectifier for Inductive Power Transfer System." Energies 12, no. 20: 3921.
This paper proposes a method to charge a lithium ion battery with an integrated compensator. Unlike the conventional charging method which uses separate voltage/current compensators based on a constant voltage-constant current charge profile, the proposed method uses a single compensator. The conventional method requires a complicated design process such as separate plant modeling for compensator design and the compensator tuning process in the frequency domain. Moreover, it has the disadvantage of a transient state between the mode change. However, the proposed method simplifies the complicated process and eliminates the transient response. The proposed compensator is applied to the LLC resonant converter and is designed to provide smooth and reliable performance during the entire charging process. In this paper, for the compensator design, the frequency domain models of the LLC resonant converter at the constant voltage and constant current charging mode are derived including the impedance model of the battery pack. Additionally, the worst condition of the compensator design during the entire charging process is considered. To demonstrate the effectiveness of the proposed method, the theoretical design procedure is presented in this paper, and it is verified through experimental results using a 300 W LLC converter and battery pack.
Yeong-Jun Choi; Hwa-Rang Cha; Sang-Min Jung; Rae-Young Kim. An Integrated Current-Voltage Compensator Design Method for Stable Constant Voltage and Current Source Operation of LLC Resonant Converters. Energies 2018, 11, 1325 .
AMA StyleYeong-Jun Choi, Hwa-Rang Cha, Sang-Min Jung, Rae-Young Kim. An Integrated Current-Voltage Compensator Design Method for Stable Constant Voltage and Current Source Operation of LLC Resonant Converters. Energies. 2018; 11 (6):1325.
Chicago/Turabian StyleYeong-Jun Choi; Hwa-Rang Cha; Sang-Min Jung; Rae-Young Kim. 2018. "An Integrated Current-Voltage Compensator Design Method for Stable Constant Voltage and Current Source Operation of LLC Resonant Converters." Energies 11, no. 6: 1325.
This paper proposes a novel active partial switching method for a boost power factor correction (PFC) converter, based on the predictive current mode control to achieve both current shaping capability and high power conversion efficiency. This method consists of a controller that maintains a switching stop angle near the peak voltage of the input voltage by means of output voltage control, and an adaptive current shaper that adjusts the switching stop period near the zero voltage of the input voltage based upon the load condition. The proposed method shows good PFC performance and high efficiency even under various disturbances such as input voltage and load fluctuations. Moreover, it has the advantage that it is possible to achieve high efficiency even under conditions of output voltage exceeding the peak value of the input voltage. For sequential explanation, this paper illustrates the design of the controller based on the frequency-domain response and provides theoretical analysis of the proposed method. Finally, to verify the effectiveness of the proposed method, experimental results are presented based upon a 2.4 kW boost PFC converter prototype.
Yeong-Jun Choi; Tae-Jin Kim; Rae-Young Kim. An Active Partial Switching Method in Tertiary Loop for a High-Efficiency Predictive Current-Mode Control PFC Converter. IEEE Transactions on Industrial Electronics 2018, 65, 7818 -7828.
AMA StyleYeong-Jun Choi, Tae-Jin Kim, Rae-Young Kim. An Active Partial Switching Method in Tertiary Loop for a High-Efficiency Predictive Current-Mode Control PFC Converter. IEEE Transactions on Industrial Electronics. 2018; 65 (10):7818-7828.
Chicago/Turabian StyleYeong-Jun Choi; Tae-Jin Kim; Rae-Young Kim. 2018. "An Active Partial Switching Method in Tertiary Loop for a High-Efficiency Predictive Current-Mode Control PFC Converter." IEEE Transactions on Industrial Electronics 65, no. 10: 7818-7828.
This paper proposes a predictive current mode control boost PFC converter adopting a novel active part switching technique to achieve both robust current shaping control to disturbances and high power conversion efficiency. This strategy consists of controlling the switching stop angle near the peak of the input voltage through the output voltage control and controlling the switching stop period near the zero voltage of the input voltage according to the load variation. The proposed method shows outstanding PFC performance and high efficiency even under various input disturbances such as input voltage and load fluctuation, and has an advantage of high efficiency even at an output voltage higher than the input voltage peak value. For sequential description, in this study, the design of the controller using the frequency domain is presented along with the theoretical analysis of the proposed method. Experimental results using a 2.4 kW boost PFC converter prototype are also presented to verify the effectiveness of the proposed method.
Yeong-Jun Choi; Rae-Young Kim; Tae-Jin Kim. A novel active discontinuous PWM control strategy for high efficiency partial switching predictive current-mode control PFC converter. 2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia (IFEEC 2017 - ECCE Asia) 2017, 236 -241.
AMA StyleYeong-Jun Choi, Rae-Young Kim, Tae-Jin Kim. A novel active discontinuous PWM control strategy for high efficiency partial switching predictive current-mode control PFC converter. 2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia (IFEEC 2017 - ECCE Asia). 2017; ():236-241.
Chicago/Turabian StyleYeong-Jun Choi; Rae-Young Kim; Tae-Jin Kim. 2017. "A novel active discontinuous PWM control strategy for high efficiency partial switching predictive current-mode control PFC converter." 2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia (IFEEC 2017 - ECCE Asia) , no. : 236-241.
The typical conventional battery charger requires the two separated voltage and current compensators to achieve both the constant current and the constant current (CC-CV) charging profile. This paper proposes a single integrated voltage-current compensator of the LLC resonant converter for lithium-ion battery charger applications. The proposed compensator is designed to provide a smooth and reliable performance during entire charging process, while providing the reduced design efforts and seamless mode transient response due to its inherent integration. The theoretical analysis and the design consideration of the proposed compensator is illustrated based on a frequency response domain, especially with the considerations of the nonlinearly varied equivalent resistor and/or effective capacitance based on the proposed battery model, and as a result, the integrated compensator guarantees a stable and robust operation. Finally several experimental results verify the effectiveness of the proposed posed compensator and its theoretical analysis.
Yeong-Jun Choi; See-Young Choi; Rae-Young Kim. An integrated voltage-current compensator of LLC resonant converter for Li-ion battery charger applications. 2016 IEEE 8th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia) 2016, 3783 -3790.
AMA StyleYeong-Jun Choi, See-Young Choi, Rae-Young Kim. An integrated voltage-current compensator of LLC resonant converter for Li-ion battery charger applications. 2016 IEEE 8th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia). 2016; ():3783-3790.
Chicago/Turabian StyleYeong-Jun Choi; See-Young Choi; Rae-Young Kim. 2016. "An integrated voltage-current compensator of LLC resonant converter for Li-ion battery charger applications." 2016 IEEE 8th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia) , no. : 3783-3790.